Method and device of MEMS process control monitoring and packaged MEMS with different cavity pressures

ABSTRACT

A method for fabricating an integrated MEMS device and the resulting structure therefore. A control process monitor comprising a MEMS membrane cover can be provided within an integrated CMOS-MEMS package to monitor package leaking or outgassing. The MEMS membrane cover can separate an upper cavity region subject to leaking from a lower cavity subject to outgassing. Differential changes in pressure between these cavities can be detecting by monitoring the deflection of the membrane cover via a plurality of displacement sensors. An integrated MEMS device can be fabricated with a first and second MEMS device configured with a first and second MEMS cavity, respectively. The separate cavities can be formed via etching a capping structure to configure each cavity with a separate cavity volume. By utilizing an outgassing characteristic of a CMOS layer within the integrated MEMS device, the first and second MEMS cavities can be configured with different cavity pressures.

CROSS-REFERENCES TO RELATED APPLICATIONS

The present application claims priority to U.S. Provisional Patentapplication No. 61/894,910, filed Oct. 23, 2013, commonly owned andincorporated by reference in its entirety.

The present application is also related to and incorporates byreference, for all purposes, the following provisional patentapplications: U.S. Provisional App. 61/835,510, filed Jun. 14, 2013,U.S. Provisional App. 61/832,657, filed Jun. 7, 2013, U.S. ProvisionalApp. 61/757,088, filed Jan. 25, 2013, and U.S. Provisional App.61/757,085, filed Jan. 25, 2013.

BACKGROUND OF THE INVENTION

The present invention is directed to MEMS(Micro-Electro-Mechanical-Systems). More specifically, embodiments ofthe invention provide methods and structure for improving integratedMEMS devices, including inertial sensors and the like.

Research and development in integrated microelectronics have continuedto produce astounding progress in CMOS and MEMS. CMOS technology hasbecome the predominant fabrication technology for integrated circuits(IC). MEMS, however, continues to rely upon conventional processtechnologies. In layman's terms, microelectronic ICs are the “brains” ofan integrated device which provides decision-making capabilities,whereas MEMS are the “eyes” and “arms” that provide the ability to senseand control the environment. Some examples of the widespread applicationof these technologies are the switches in radio frequency (RF) antennasystems, such as those in the iPhone™ device by Apple, Inc. ofCupertino, Calif., and the Blackberry™ phone by Research In MotionLimited of Waterloo, Ontario, Canada, and accelerometers insensor-equipped game devices, such as those in the Wii™ controllermanufactured by Nintendo Company Limited of Japan. Though they are notalways easily identifiable, these technologies are becoming ever moreprevalent in society every day.

Beyond consumer electronics, use of IC and MEMS has limitlessapplications through modular measurement devices such as accelerometers,gyroscopes, actuators, and sensors. In conventional vehicles,accelerometers and gyroscopes are used to deploy airbags and triggerdynamic stability control functions, respectively. MEMS gyroscopes canalso be used for image stabilization systems in video and still cameras,and automatic steering systems in airplanes and torpedoes. BiologicalMEMS (Bio-MEMS) implement biosensors and chemical sensors forLab-On-Chip applications, which integrate one or more laboratoryfunctions on a single millimeter-sized chip only. Other applicationsinclude Internet and telephone networks, security and financialapplications, and health care and medical systems. As describedpreviously, ICs and MEMS can be used to practically engage in varioustype of environmental interaction.

Although highly successful, ICs and in particular MEMS still havelimitations. Similar to IC development, MEMS development, which focuseson increasing performance, reducing size, and decreasing cost, continuesto be challenging. Additionally, applications of MEMS often requireincreasingly complex microsystems that desire greater computationalpower. Unfortunately, such applications generally do not exist. Theseand other limitations of conventional MEMS and ICs may be furtherdescribed throughout the present specification and more particularlybelow.

From the above, it is seen that techniques for improving fabricationtechniques for IC devices and MEMS are highly desired.

BRIEF SUMMARY OF THE INVENTION

The present invention is directed to integrated MEMS(Micro-Electro-Mechanical-Systems) IC (Integrated Circuit) devices. Morespecifically, embodiments of the invention provide a methods forfabricating an integrated MEMS devices with different cavity pressuresand a pressure control monitor. Merely by way of example, the MEMSdevice can include at least an accelerometer, a gyroscope, a magneticsensor, a pressure sensor, a microphone, a humidity sensor, atemperature sensor, a chemical sensor, a biosensor, an inertial sensor,and others. But it will be recognized that the invention has a muchgreater range of applicability.

One of the most critical factors in the process control of MEMS devicesoperating under vacuum conditions is the air pressure inside capping orpackage cavities. These kinds of MEMS devices include gyroscopes,resonators, and other like devices. One of the primary process issuesthat degrade the vacuum conditions of these devices involve leaking atcapping/package interfaces and outgassing from inside capping or packagecavities.

From a process control point of view, one of the most importantpractices used to improve vacuum conditions from MEMS devices is toidentify and decouple abnormal leaking and outgassing in the MEMSfabrication process. Once identified, appropriate correcting processfixes or tunings can be applied. However, identifying such issues isextremely challenging as vacuum degradation from leaking and outgassingcannot be distinguished readily by prior vacuum sensitive structures,such as gyroscopes, resonators, or Pirani gauges and the like.Additionally, the physical and electrical failure analysis for suchdevices is difficult, especially in cases of fine leaking andoutgassing. Embodiments of the present invention provide methods formonitoring MEMS device fabrication processes and structures forintegrated MEMS devices having pressure control monitors.

In integrated MEMS design, certain MEMS devices require differentoperating air pressures, some examples being a gyroscope and anaccelerometer. This means that a package with two MEMS devices requiringdifferent operating pressures will require either separated MEMSpackages or a single MEMS package with different packaging pressures.Both design approaches are challenging and complex, which tends to leadto low production yield. Addressing this design issue is a major key indeveloping a successful integrated multiple MEMS device, such as anintegrated MEMS gyroscope and accelerometer.

A single MEMS package design is desirable as it provides a smaller formfactor, smaller die size, and better process complexity. However,implementing different package pressures during a single MEMS packagingprocess can be extremely difficult. For example, using conformalthin-film enclosures of separated package cavities is not mechanicallyor process-oriented robust. Embodiments of the present invention providea method and structure for a single MEMS package with different vacuumpressures using intrinsic outgassing. The outgassing can come fromexposed CMOS layers that are enclosed in a package cavity. In a specificembodiment, intrinsic outgassing can be used to create different finalcavity air pressures in separated package cavities with significantlydifferent volumes.

Many benefits are achieved by way of embodiments of the presentinvention over conventional techniques. Methods and structures of aprocess control monitor can be used to identify and decouple abnormalleaking and outgassing in the MEMS fabrication process. This allows forappropriate correcting process fixes or tunings to applied be applied,which can improve device performance and production yield. Methods andstructures of an integrated multiple MEMS device having different cavitypressures allow multiple MEMS devices to be integrated on a single chipwhile maintaining separate cavity environments with appropriateoperating air pressures. Depending upon the embodiment, one or more ofthese benefits may be achieved. These and other benefits will bedescribed in more detail throughout the present specification and moreparticularly below.

Various additional objects, features, and advantages of the presentinvention can be more fully appreciated with reference to the detaileddescription and accompanying drawings that follow.

BRIEF DESCRIPTION OF THE DRAWINGS

In order to more fully understand the present invention, reference ismade to the accompanying drawings. Understanding that these drawings arenot to be considered limitations in the scope of the invention, thepresently described embodiments and the presently understood best modeof the invention are described with additional detail through use of theaccompanying drawings in which:

FIG. 1 illustrates a simplified diagram of an integrated MEMS deviceaccording to an embodiment of the present invention.

FIGS. 2-4 illustrates simplified diagrams of an integrated MEMS deviceusing a Process Control Monitor according to an embodiment of thepresent invention.

FIG. 5 illustrates a simplified flow diagram of a method for forming apressure control sensor according to an embodiment of the presentinvention.

FIG. 6 illustrates a simplified diagram of an integrated multiple MEMSdevice within a single package having a single cavity pressure accordingto an embodiment of the present invention.

FIGS. 7 and 8 illustrate simplified diagrams of an integrated multipleMEMS device within a single package having separate cavity pressuresaccording to an embodiment of the present invention.

FIG. 9 illustrates a simplified flow diagram of a method for fabricatingan integrated MEMS device having separate cavity pressures according toan embodiment of the present invention; and

FIG. 10 illustrates a simplified functional block diagram of variousembodiments of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

The present invention is directed to integrated MEMS(Micro-Electro-Mechanical-Systems) IC (Integrated Circuit) devices. Morespecifically, embodiments of the invention provide a method andstructure for a MEMS fabrication, including one or more discrete MEMSdevices. Merely by way of example, the MEMS device can include at leastan accelerometer, a gyroscope, a magnetic sensor, a pressure sensor, amicrophone, a humidity sensor, a temperature sensor, a chemical sensor,a biosensor, an inertial sensor, and others. But it will be recognizedthat the invention has a much greater range of applicability.

FIG. 1 illustrates a simplified diagram of an integrated MEMS deviceaccording to an embodiment of the present invention. This figure shows across-sectional view of an integrated MEMS device with potential leakingregions and potential outgassing regions. Device 100 is configured frombottom to top with the following device layers: a semiconductorsubstrate 110, a material layer 120, a MEMS material layer 130, aninterface layer 140, and a cap layer 150. Those of ordinary skill in theart will recognize other variations, modifications, and alternatives.

In an embodiment, the semiconductor substrate 110 can be a CMOSsubstrate having a plurality of CMOS devices formed thereon. Thesemiconductor substrate 110 can have an upper surface region, which canbe associated with an outgassing characteristic. The material layer 120overlies the substrate 110 and can include a dielectric material withlower cavity region or lower volumetric cavity. The interface layer 140can include a WLP (Wafer Level Packaging) material layer. The MEMS layer130 overlies the lower volumetric cavity and the cap layer 150 enclosesan upper volumetric cavity. In this embodiment, the upper volumetriccavity and the lower volumetric cavity are connected through openings inthe MEMS layer 130.

One of the most critical factors in the process control of MEMS devicesoperating under vacuum conditions is the air pressure inside capping orpackage cavities. These kinds of MEMS devices include gyroscopes,resonators, and other like devices. One of the primary process issuesthat degrade the vacuum conditions of these devices involve leaking atcapping/package interfaces and outgassing from inside capping or packagecavities. Here, potential leaking regions 101 and potential outgassingregions 102 are shown within a vicinity of the interface layer 140 andwithin a vicinity of the upper surface region of the CMOS substrate 110,respectively.

From a process control point of view, one of the most importantpractices used to improve vacuum conditions from MEMS devices is toidentify and decouple abnormal leaking and outgassing in the MEMSfabrication process. Once identified, appropriate correcting processfixes or tunings can be applied. However, identifying such issues isextremely challenging as vacuum degradation from leaking and outgassingcannot be distinguished readily by prior vacuum sensitive structures,such as gyroscopes, resonators, or Pirani gauges and the like.Additionally, the physical and electrical failure analysis for suchdevices is difficult, especially in cases of fine leaking andoutgassing. Embodiments of the present invention provide methods formonitoring MEMS device fabrication processes and structures forintegrated MEMS devices having pressure control monitors.

FIG. 2 illustrates a simplified diagram of an integrated MEMS deviceusing a Process Control Monitor according to an embodiment of thepresent invention. This figure shows a cross-sectional view of anintegrated MEMS device 200, which is configured from bottom to top withthe following device layers: a semiconductor substrate 210, a materiallayer 220, a MEMS material layer 230, an interface layer 240, and a caplayer 250. Those of ordinary skill in the art will recognize othervariations, modifications, and alternatives.

In an embodiment, the semiconductor substrate 210 can be a CMOSsubstrate having a plurality of CMOS devices formed thereon. Thesemiconductor substrate 210 can have an upper surface region, which canbe associated with an outgassing characteristic. The material layer 220overlies the substrate 210 and can include a dielectric material withlower cavity region or lower volumetric cavity. In a specificembodiment, the material layer 220 can include sidewall structures thatare configured on semiconductor substrate 210. These sidewall structurescan enable definition of the lower volumetric cavity.

The interface layer 240 can include a WLP material, which can be abonding interface that is associated with a leakage characteristic. TheMEMS layer 230 can include a membrane cover that overlies the lowercavity region. The membrane cover can have an upper surface and a lowersurface and can be disposed upon at least a portion of the semiconductorsubstrate 210. The membrane cover can be formed upon a portion of thesemiconductor substrate 210 within a first low pressure environment,which can be a vacuum. In a specific embodiment, the lower surface ofthe membrane cover and a portion of the upper surface of thesemiconductor substrate enable definition of a lower volumetric cavity,which can include the lower cavity region.

The cap layer 250 can include a capping structure having a lowersurface, which can be coupled to the membrane cover at the interfacelayer 240. The capping structure can be coupled to the membrane coverwithin a second low pressure environment. The first low pressureenvironment can be substantially similar to the second low pressureenvironment. In a specific embodiment, the capping structure can beformed from another semiconductor substrate and the capping structurecan include a plurality of sidewall structures 253. These sidewallstructures can enable definition of the upper volumetric cavity. In aspecific embodiment, the upper surface of the membrane cover and thelower surface of the capping structure can enable definition of an uppervolumetric cavity, which can include the upper cavity region. In thisembodiment, the upper volumetric cavity and the lower volumetric cavityare connected through openings in the MEMS layer 230.

In a specific embodiment, a plurality of displacement sensors 260 can beconfigured adjacent to the membrane cover. The plurality of displacementsensors can be configured to determine a displacement of the membranecover towards to upper volumetric cavity or towards the lower volumetriccavity. The plurality of displacement sensors can include capacitors,movable electrodes, fixed electrodes, and the like.

In this embodiment, the upper volumetric cavity and the lower volumetricare separated a process control monitor structure which can include themembrane layer. The membrane layer covers and encloses major exposedareas of the CMOS layers in the CMOS substrate 210. The pressure of theupper volumetric cavity and the lower volumetric cavity divided by themembrane are the same without leaking or outgassing, which means nopressure difference is applied and thus the membrane 220 will not bedeformed. In a specific embodiment, an initial gas pressure of the lowervolumetric cavity and an initial gas pressure of the lower volumetriccavity are substantially similar.

FIG. 3 illustrates a simplified diagram of an integrated MEMS deviceusing a Process Control Monitor according to an embodiment of thepresent invention. This figure shows a cross-sectional view of anintegrated MEMS device 300 similar to that of FIG. 2. Device 300configured from bottom to top with the following device layers: asemiconductor substrate 310, a material layer 320, a MEMS material layer330, an interface layer 340, and a cap layer 350. Specific detailsregarding these elements are described previously for device 200 of FIG.2.

Compared to device 200 of FIG. 2, device 300 shows leakage at theinterface layer 340, which degrades the vacuum of the upper cavityregion or upper volumetric cavity. This degradation renders the pressureof the upper cavity region higher than that of the lower cavity regionor lower volumetric cavity, which results in an applied downward forceon the membrane 330 due to the pressure difference. The downward forcecauses the membrane to deform and deflect towards the lower cavityregion. Here, the upper volumetric cavity and the lower volumetriccavity can have dissimilar volumes. In a specific embodiment, the MEMSmembrane layer 320 can include one or more displacement sensors 360,which can include capacitors. The deformation of the membrane 320 can beread out by the change in capacitance of the displacement sensors.

FIG. 4 illustrates a simplified diagram of an integrated MEMS deviceusing a Process Control Monitor according to an embodiment of thepresent invention. This figure shows a cross-sectional view of anintegrated MEMS device 400 similar to that of FIG. 2. Device 400configured from bottom to top with the following device layers: asemiconductor substrate 410, a material layer 420, a MEMS material layer430, an interface layer 440, and a cap layer 450. Specific detailsregarding these elements are described previously for device 200 of FIG.2.

Compared to device 200 of FIG. 2, device 400 shows outgassing from theCMOS layers of the CMOS substrate 410, which degrades the vacuum of theupper cavity region or upper volumetric cavity. This degradation rendersthe pressure of the lower cavity region or lower volumetric cavityhigher than that of the upper cavity region, which results in an appliedupward force on the membrane 430 due to the pressure difference. Theupward force causes the membrane to deform and deflect towards the uppercavity region. Similar to the previous embodiment, the MEMS membranelayer 430 can include one or more displacement sensors 460, which caninclude capacitors. The deformation of the membrane 420 can be read outby the change in capacitance of the displacement sensors.

Process control and improvement are key elements of MEMS productdevelopment that contribute to a majority of development time as MEMSproducts are highly sensitive and coupled with critical processparameters. For example, one of the most critical process parameters forthe gyroscope is air pressure inside a capping/package cavity, but theprimary process issues involve degrading vacuum conditions due toleaking at capping/package interfaces and outgassing insidecapping/package cavities. Being able to identify/decouple abnormalleaking and outgassing in the MEMS process and production allows forcorrecting fixes/tuning to be applied, which will significantly reduceundesirable factors such as developmental efforts and time to market.

Embodiments of the present invention provide a Process Control Monitordesign for MEMS package leaking and outgassing. The Process ControlMonitor can monitor and distinguish vacuum degradation from leakingversus outgassing. The Process Control Monitor can include a MEMSmembrane inside a capping structure. The membrane can divide an upperand lower cavity and can be used to distinguish vacuum degradation fromleaking at WLP interface regions or from outgassing of the CMOS layers.

FIG. 5 is a simplified flow diagram of a method for forming a pressurecontrol sensor according to an embodiment of the present invention. Asshown, the method 500 can include the following steps:

-   -   502. receive a semiconductor substrate having a plurality of        CMOS devices formed thereon, wherein the semiconductor substrate        includes an upper surface, and wherein the upper surface of the        semiconductor substrate is associated with an outgassing        characteristic;    -   504. form sidewall structures upon the semiconductor substrate,        wherein the sidewall structures formed upon the semiconductor        substrate enable definition of a lower volumetric cavity;    -   506. form a membrane cover upon at least a portion of the        semiconductor substrate, wherein the membrane cover includes an        upper surface and a lower surface, wherein the lower surface of        the membrane cover and a portion of the upper surface of the        semiconductor substrate enable definition of the lower        volumetric cavity;    -   508. form a plurality of displacement sensors adjacent to the        membrane cover, wherein the plurality of displacement sensors        are configured to determine a displacement of the membrane cover        towards the upper or lower volumetric cavities;    -   510. couple a capping structure to the membrane cover at a        bonding interface, wherein the bonding interface is associated        with a leakage characteristic, wherein the capping structure        includes a lower surface, wherein the upper surface of the        membrane cover and lower surface of the capping structure enable        definition of an upper volumetric cavity;    -   512. report a change in pressure detected by the plurality of        displacement sensors by a change in capacitance values; and    -   514. Other steps as desired.

These steps are merely examples and should not unduly limit the scope ofthe claims herein. One of ordinary skill in the art would recognize manyother variations, modifications, and alternatives. For example, varioussteps outlined above may be added, removed, modified, rearranged,repeated, and/or overlapped, as contemplated within the scope of theinvention.

In an embodiment, the present invention provides a method of fabricatingan process control monitor for an integrated MEMS device. The method 500includes receiving a semiconductor substrate, step 502, having an uppersurface that is associated with an outgassing characteristic. Thissubstrate can have a plurality of CMOS devices formed thereon. Sidewallstructures can be formed upon the semiconductor substrate, step 504.These sidewall structures can enable the definition of a lowervolumetric cavity.

A membrane cover can be formed upon at least a portion of thesemiconductor substrate, step 506. The membrane cover can be formedwithin a first low pressure environment, which can be approximately avacuum. This membrane cover can include an upper surface and a lowersurface. The lower surface of the membrane cover and a portion of theupper surface of the semiconductor substrate can enable the definitionof the lower volumetric cavity. A plurality of displacement sensors canbe formed adjacent to the membrane cover, step 508. The plurality ofdisplacement sensors can be configured to determine a displacement ofthe membrane cover towards the upper volumetric cavity or towards thelower volumetric cavity. In a specific embodiment, the plurality ofdisplacement sensors can include capacitors.

A capping structure with a lower surface can be coupled to the membranecover at a bonding interface, step 510. The bonding interface can beassociated with a leakage characteristic. The coupling of the cappingstructure can occur within a second low pressure environment. The uppersurface of the membrane cover and the lower surface of the cappingstructure can enable the definition of an upper volumetric cavity. Aninitial gas pressure of the lower volumetric cavity and an initial gaspressure of the upper volumetric cavity can be substantially similar ordissimilar depending on the leaking and outgassing present within thedevice. If a displacement indicating a change in pressure is detected,this change can be reported by an output of change in capacitance valuesby the plurality of displacement sensors, step 512. Other details can befound in the descriptions for FIGS. 2-4. Other steps can be performed asdesired, step 514.

FIG. 6 illustrates a simplified diagram of an integrated multiple MEMSdevice within a single package having a single cavity pressure accordingto an embodiment of the present invention. This figure shows across-sectional view of an integrated MEMS device 600 similar to that ofFIG. 2 with more than one MEMS device. Device 600 configured from bottomto top with the following device layers: a semiconductor substrate 610,a material layer 620, a MEMS material layer 630, an interface layer 640,and a cap layer 650. The MEMS layer 630 includes a first MEMS 631 and asecond MEMS 632, which can be a gyroscope and accelerometer,respectively, or any other pair of MEMS devices. The interface layer 640between the cap layer 650 and the MEMS layer 630 can be a WLP layerhaving an interface region. Here, the cap layer 650 encloses the firstand second MEMS 631, 632 in a single cavity, thus sharing the samecavity pressure.

In integrated MEMS design, certain MEMS devices require differentoperating air pressures, some examples being a gyroscope and anaccelerometer. This means that a package with two MEMS devices requiringdifferent operating will require either separated MEMS packages or asingle MEMS package with different packaging pressures. Both designapproaches are challenging and complex, which tends to lead to lowproduction yield. Addressing this design issue is a major key indeveloping a successful integrated multiple MEMS device, such as anintegrated MEMS gyroscope and accelerometer.

A single MEMS package design is desirable as it provides a smaller formfactor, smaller die size, and better process complexity. However,implementing different package pressures during a single MEMS packagingprocess can be extremely difficult. For example, using conformalthin-film enclosures of separated package cavities is not mechanicallyor process-oriented robust. Embodiments of the present invention providea method and structure for a single MEMS package with different vacuumpressures using intrinsic outgassing. The outgassing can come fromexposed CMOS layers that are enclosed in a package cavity, as describedin FIG. 1. In a specific embodiment, intrinsic outgassing can be used tocreate different final cavity air pressures in separated packagecavities with significantly different volumes.

FIG. 7 illustrates a simplified diagram of an integrated multiple MEMSdevice within a single package having separate cavity pressuresaccording to an embodiment of the present invention. This figure shows across-sectional view of an integrated MEMS device 700 similar to that ofFIG. 6, but with separate package cavities. Device 700 configured frombottom to top with the following device layers: a semiconductorsubstrate 710, a material layer 720, a MEMS material layer 730, aninterface layer 740, and a cap layer 750. The MEMS layer 730 includes afirst MEMS 731 and a second MEMS 732, which can be a gyroscope andaccelerometer, respectively, or any other pair of MEMS devices.

The cap layer 750 includes a first cap 751 and a second cap 752. Thesecond cap 752 is configured overlying the second MEMS 732 and the firstcap 751 is configured overlying the first and second MEMS 731 and 732,as well as the second cap 752. The interface layer 740 between the caplayer 750 and the MEMS layer 730 can be a WLP layer having an interfaceregion. Here, the second cap 752 encloses the second MEMS 732 in asecond cavity that is separate from the first cavity wherein the firstMEMS 731 is enclosed.

In a specific embodiment, the first MEMS 731 and the second MEMS 732,which are separated in different cavities, are exposed to differentcavity air pressures due to the different cavity heights. For example,the second cavity with the second MEMS 732 has a lower cavity height,which results in a smaller cavity volume. By comparison, the firstcavity with the first MEMS 731 has a higher cavity height, which resultsin a large cavity volume.

FIG. 8 illustrates a simplified diagram of an integrated multiple MEMSdevice within a single package having separate cavity pressuresaccording to an embodiment of the present invention. This figure shows across-sectional view of an integrated MEMS device 800 similar to that ofFIG. 7. Device 800 configured from bottom to top with the followingdevice layers: a semiconductor substrate 810, a material layer 820, aMEMS material layer 830, an interface layer 840, and a cap layer 850.Those of ordinary skill in the art will recognize other variations,modifications, and alternatives.

The semiconductor substrate 810 includes a plurality of CMOS devicesformed thereon and also includes an upper surface, which can beassociated with an outgassing characteristic. The interface layer 820can include a dielectric material layer, which can be disposed upon thesemiconductor substrate 810 and can include a plurality of cavitiesformed thereon. The plurality of cavities includes a first lower cavity821 and a second lower cavity 822, which expose portions of the uppersurface of the semiconductor substrate 810. The MEMS material layer 830includes a first MEMS 831 and a second MEMS 832, which can be agyroscope and accelerometer, respectively, or any other pair of MEMSdevices. The first MEMS 831 can be configured adjacent to the firstlower cavity 821 and the second MEMS 832 can be configured adjacent tothe second lower cavity 822.

The cap layer 850 can include a capping structure disposed above theinterface layer 830, which can be a dielectric material layer. Thecapping structure can comprise a plurality of caps including a firstupper cap 851 and a second upper cap 852. A bonding interface layer 840is shown between the cap layer and the MEMS layer. In a specificembodiment, the capping structure can be coupled to the MEMS materiallayer 830 at the bonding interface layer 840. The second cap 852 isconfigured overlying the second MEMS 832 and the first cap 851 isconfigured overlying the first and second MEMS 831 and 832, as well asthe second cap 852.

In a specific embodiment, the capping structure includes a cappingsubstrate having a surface and a dielectric layer disposed above asurface of the capping structure. The plurality of cap regions can beetched within the dielectric layer to expose portions of the surface ofthe capping substrate and to form the first cap region and the secondcap region. In another embodiment, the first cap region is etched withinthe dielectric layer to expose portions of the surface of the cappingsubstrate, but the second cap region does not expose portions of thesurface of the capping substrate. Furthermore, a wafer-level bondingmaterial can be disposed between the capping structure and thedielectric material.

The first upper cap 851 and the first lower cavity 821 can form a firstMEMS cavity with the first MEMS 831 disposed therein. The second uppercap 852 and the second lower cavity 822 can form a second MEMS cavitywith the second MEMS 832 disposed therein. In another embodiment, thecapping structure can include a plurality of cap regions including afirst cap region 861 and a second cap region 862. In this case, thefirst cap region 861 and the first lower cavity 821 form the first MEMScavity and the second cap region 862 and the second lower cavity 822form the second MEMS cavity. The first and second MEMS cavities areseparate from each other.

In an embodiment, the outgassing characteristic of the semiconductorsubstrate 810 can be utilized to form different cavity pressures or gaspressures within the separate MEMS cavities. An initial gas pressure ofthe first MEMS cavity and the initial gas pressure of the second MEMScavity can be substantially similar. However, the volume of the firstMEMS cavity can be different from that of the second MEMS cavity whilethe volume of the first lower cavity can be substantially similar to thevolume of the second lower cavity. In a specific embodiment, the volumeof the second cap region is less than a volume of the first cap region.This difference in volume can be due to the second cap region having adepth or height that is less than that of the first cap region.

The large cavity volume for the first MEMS 831 can have a desirable lowpressure with minimal air pressure contributed by outgassing. Bycomparison, the small cavity volume of the second MEMS 832 can have adesirable high pressure with maximal air pressure contributed byoutgassing. Varying levels of cavity air pressures can be created withinseparate cavity regions created by different cap structures havingdifferent cavity heights. Of course, there can be other variations,modifications, and alternatives.

FIG. 9 illustrates a simplified flow diagram of a method for fabricatingan integrated MEMS device having separate cavity pressures according toan embodiment of the present invention. As shown, the method 900 caninclude the following steps:

-   -   902. receive a semiconductor substrate having a plurality of        CMOS devices formed thereon, wherein the semiconductor substrate        includes an upper surface, and wherein the upper surface of the        semiconductor substrate is associated with an outgassing        characteristic;    -   904. form a material layer on top of the semiconductor        substrate, wherein the material layer includes a first lower        cavity and a second lower cavity;    -   906. form a MEMS material layer comprising a first MEMS device        on top of the first lower cavity and a second MEMS device on top        of the second lower cavity;    -   908. form a capping structure comprising a plurality of caps        including a first upper cap and a second upper cap;    -   910. couple the capping structure to the MEMS material layer at        a bonding interface, wherein the first upper cap and first lower        cavity form a first MEMS cavity, wherein the first MEMS device        is disposed therein, wherein the second upper cap and the second        lower cavity form a second MEMS cavity, wherein the second MEMS        device is disposed therein, wherein the first MEMS cavity is        separate from the second MEMS cavity; and    -   912. Other steps as desired.

These steps are merely examples and should not unduly limit the scope ofthe claims herein. One of ordinary skill in the art would recognize manyother variations, modifications, and alternatives. For example, varioussteps outlined above may be added, removed, modified, rearranged,repeated, and/or overlapped, as contemplated within the scope of theinvention.

In an embodiment, the present invention provides a method of fabricatingan integrated MEMS device. The method 900 can include receiving asemiconductor substrate having a plurality of CMOS devices formedthereon, step 902. The semiconductor substrate can include an uppersurface, which is associated with an outgassing characteristic.

A material layer can be formed on top of the semiconductor substrate,step 904. The material layer can include a first lower cavity and asecond lower cavity. Forming the material layer can include forming adielectric layer above the upper surface of the semiconductor substrate.The portions of the dielectric layer can be etched to expose portions ofthe upper surface of the semiconductor substrate and to form the firstlower cavity and the second lower cavity. A MEMS material layer can beformed on top of the semiconductor substrate, step 906. The MEMSmaterial layer can include a first MEMS device on top of the first lowercavity and a second MEMS device on top of the second lower cavity. In aspecific embodiment, the first MEMS can be a gyroscope and the secondMEMS can be an accelerometer.

A capping structure can be formed with a plurality of caps, which caninclude a first upper cap and a second upper cap, step 908. Forming thecapping structure can include receiving a capping substrate and forminga dielectric layer above a surface of the capping substrate. Portions ofthis dielectric layer can be etched to expose portions of the surface ofthe capping substrate and to form the first upper cap and the secondupper cap. In another embodiment, portions of the dielectric layer canbe etched to expose portions of the surface of the capping substrate andto form the first upper cap. However, the second upper cap is notexposed to portions of the surface of the capping structure. In variousembodiments, the depths or heights of the first upper cap and the secondupper cap can be controlled by the etching process.

The capping structure can be coupled to the MEMS material layer at abonding interface, step 910. The first upper cap and the first lowercavity can form a first MEMS cavity with the first MEMS device disposedtherein. The second upper cap and the second lower cavity form a secondMEMS cavity with the second MEMS device disposed therein. The first MEMScavity is separate from the second MEMS cavity.

An initial gas pressure of the first MEMS cavity and an initial gaspressure of the second MEMS cavity can be substantially similar. Also, avolume of the first lower cavity can be substantially similar to avolume of the second lower cavity. However, a volume of the first MEMScavity can be different from a volume of the second MEMS cavity. In aspecific embodiment, the volume difference can be due to a volume of thesecond upper cap being less than a volume of the first upper cap.Specifically, a depth of the second upper cap can be less than a depthof the first upper cap, which can be due to the etching of a dielectriclayer formed above a surface of a capping substrate, as describedpreviously.

The outgassing characteristic of the semiconductor substrate causes agas pressure of the first MEMS cavity to be different from a gaspressure of the second MEMS cavity. This allows each MEMS device withinits respective cavity to operate at separate cavity air pressures. Othersteps can be performed as desired, step 912.

FIG. 10 illustrates a functional block diagram of various embodiments ofthe present invention. In FIG. 10, a computing device 1000 typicallyincludes an applications processor 1010, memory 1020, a touch screendisplay 1030 and driver 1040, an image acquisition device 1050, audioinput/output devices 1060, and the like. Additional communications fromand to computing device are typically provided by via a wired interface1070, a GPS/Wi-Fi/Bluetooth interface 1080, RF interfaces 1090 anddriver 1100, and the like. Also included in various embodiments arephysical sensors 1110.

In various embodiments, computing device 1000 may be a hand-heldcomputing device (e.g. Apple iPad, Apple iTouch, Dell Mini slate, LenovoSkylight/IdeaPad, Asus EEE series, Microsoft Courier, Notion Ink Adam),a portable telephone (e.g. Apple iPhone, Motorola Droid, Google NexusOne, HTC Incredible/EVO 4G, Palm Pre series, Nokia N900), a portablecomputer (e.g. netbook, laptop), a media player (e.g. Microsoft Zune,Apple iPod), a reading device (e.g. Amazon Kindle, Barnes and NobleNook), or the like.

Typically, computing device 1000 may include one or more processors1010. Such processors 1010 may also be termed application processors,and may include a processor core, a video/graphics core, and othercores. Processors 1010 may be a processor from Apple (A4), Intel (Atom),NVidia (Tegra 2), Marvell (Armada), Qualcomm (Snapdragon), Samsung, TI(OMAP), or the like. In various embodiments, the processor core may bean Intel processor, an ARM Holdings processor such as the Cortex-A, -M,-R or ARM series processors, or the like. Further, in variousembodiments, the video/graphics core may be an Imagination Technologiesprocessor PowerVR-SGX, -MBX, -VGX graphics, an Nvidia graphics processor(e.g. GeForce), or the like. Other processing capability may includeaudio processors, interface controllers, and the like. It iscontemplated that other existing and/or later-developed processors maybe used in various embodiments of the present invention.

In various embodiments, memory 1020 may include different types ofmemory (including memory controllers), such as flash memory (e.g. NOR,NAND), pseudo SRAM, DDR SDRAM, or the like. Memory 1020 may be fixedwithin computing device 1000 or removable (e.g. SD, SDHC, MMC, MINI SD,MICRO SD, CF, SIM). The above are examples of computer readable tangiblemedia that may be used to store embodiments of the present invention,such as computer-executable software code (e.g. firmware, applicationprograms), application data, operating system data or the like. It iscontemplated that other existing and/or later-developed memory andmemory technology may be used in various embodiments of the presentinvention.

In various embodiments, touch screen display 1030 and driver 1040 may bebased upon a variety of later-developed or current touch screentechnology including resistive displays, capacitive displays, opticalsensor displays, electromagnetic resonance, or the like. Additionally,touch screen display 1030 may include single touch or multiple-touchsensing capability. Any later-developed or conventional output displaytechnology may be used for the output display, such as TFT-LCD, OLED,Plasma, trans-reflective (Pixel Qi), electronic ink (e.g.electrophoretic, electrowetting, interferometric modulating). In variousembodiments, the resolution of such displays and the resolution of suchtouch sensors may be set based upon engineering or non-engineeringfactors (e.g. sales, marketing). In some embodiments of the presentinvention, a display output port, such as an HDMI-based port orDVI-based port may also be included.

In some embodiments of the present invention, image capture device 1050may include a sensor, driver, lens and the like. The sensor may be basedupon any later-developed or convention sensor technology, such as CMOS,CCD, or the like. In various embodiments of the present invention, imagerecognition software programs are provided to process the image data.For example, such software may provide functionality such as: facialrecognition, head tracking, camera parameter control, or the like.

In various embodiments, audio input/output 1060 may include conventionalmicrophone(s)/speakers. In some embodiments of the present invention,three-wire or four-wire audio connector ports are included to enable theuser to use an external audio device such as external speakers,headphones or combination headphone/microphones. In various embodiments,voice processing and/or recognition software may be provided toapplications processor 1010 to enable the user to operate computingdevice 1000 by stating voice commands. Additionally, a speech engine maybe provided in various embodiments to enable computing device 1000 toprovide audio status messages, audio response messages, or the like.

In various embodiments, wired interface 1070 may be used to provide datatransfers between computing device 1000 and an external source, such asa computer, a remote server, a storage network, another computing device1000, or the like. Such data may include application data, operatingsystem data, firmware, or the like. Embodiments may include anylater-developed or conventional physical interface/protocol, such as:USB 2.0, 3.0, micro USB, mini USB, Firewire, Apple iPod connector,Ethernet, POTS, or the like. Additionally, software that enablescommunications over such networks is typically provided.

In various embodiments, a wireless interface 1080 may also be providedto provide wireless data transfers between computing device 1000 andexternal sources, such as computers, storage networks, headphones,microphones, cameras, or the like. As illustrated in FIG. 10, wirelessprotocols may include Wi-Fi (e.g. IEEE 802.11a/b/g/n, WiMax), Bluetooth,IR and the like.

GPS receiving capability may also be included in various embodiments ofthe present invention, however is not required. As illustrated in FIG.10, GPS functionality is included as part of wireless interface 1080merely for sake of convenience, although in implementation, suchfunctionality is currently performed by circuitry that is distinct fromthe Wi-Fi circuitry and distinct from the Bluetooth circuitry.

Additional wireless communications may be provided via RF interfaces1090 and drivers 1100 in various embodiments. In various embodiments, RFinterfaces 1090 may support any future-developed or conventional radiofrequency communications protocol, such as CDMA-based protocols (e.g.WCDMA), GSM-based protocols, HSUPA-based protocols, or the like. In theembodiments illustrated, driver 1100 is illustrated as being distinctfrom applications processor 1010. However, in some embodiments, thesefunctionality are provided upon a single IC package, for example theMarvel PXA330 processor, and the like. It is contemplated that someembodiments of computing device 1000 need not include the RFfunctionality provided by RF interface 1090 and driver 1100.

FIG. 10 also illustrates computing device 1000 to include physicalsensors 1110. In various embodiments of the present invention, physicalsensors 1110 can be single axis or multi-axis Micro-Electro-MechanicalSystems (MEMS) based devices being developed by M-cube, the assignee ofthe present patent application. Physical sensors 1110 can includeaccelerometers, gyroscopes, pressure sensors, magnetic field sensors,bio sensors, and the like. In other embodiments of the presentinvention, conventional physical sensors 1110 from Bosch,STMicroelectronics, Analog Devices, Kionix or the like may be used.

In various embodiments, any number of future developed or currentoperating systems may be supported, such as iPhone OS (e.g. iOS),WindowsMobile (e.g. 7), Google Android (e.g. 2.2), Symbian, or the like.In various embodiments of the present invention, the operating systemmay be a multi-threaded multi-tasking operating system. Accordingly,inputs and/or outputs from and to touch screen display 1030 and driver1040 and inputs/or outputs to physical sensors 1110 may be processed inparallel processing threads. In other embodiments, such events oroutputs may be processed serially, or the like. Inputs and outputs fromother functional blocks may also be processed in parallel or serially,in other embodiments of the present invention, such as image acquisitiondevice 1050 and physical sensors 1110.

FIG. 10 is representative of one computing or micro-processing device1000 capable of embodying the present invention. The previouslydescribed methods of operation can be implemented with on-chip logic orthrough a micro-processor in the same device or in a separate chipwithin the hand-held device. It will be readily apparent to one ofordinary skill in the art that many other hardware and softwareconfigurations are suitable for use with the present invention.Embodiments of the present invention may include at least some but neednot include all of the functional blocks illustrated in FIG. 10. Forexample, in various embodiments, computing device 1000 may lack imageacquisition unit 1050, or RF interface 1090 and/or driver 1100, or GPScapability, or the like. Additional functions may also be added tovarious embodiments of computing device 1000, such as a physicalkeyboard, an additional image acquisition device, a trackball ortrackpad, a joystick, or the like. Further, it should be understood thatmultiple functional blocks may be embodied into a single physicalpackage or device, and various functional blocks may be divided and beperformed among separate physical packages or devices.

According to some embodiment of the present invention, a method forforming a pressure control monitor includes receiving a semiconductorsubstrate having a plurality of CMOS devices formed thereon, wherein thesemiconductor substrate includes an upper surface, and wherein the uppersurface of the semiconductor substrate is associated with an outgassingcharacteristic. The method also includes forming a membrane cover uponat least a portion of the semiconductor substrate, wherein the membranecover includes an upper surface and a lower surface, wherein the lowersurface of the membrane cover and a portion of the upper surface of thesemiconductor substrate enable definition of a lower volumetric cavity.The method also includes coupling a capping structure to the membranecover at a bonding interface, wherein the bonding interface isassociated with a leakage characteristic, wherein the capping structureincludes a lower surface, wherein the upper surface of the membranecover and lower surface of the capping structure enable definition of anupper volumetric cavity. In an embodiment, the upper volumetric cavityand the lower volumetric cavity are separated by the membrane cover. Inanother embodiment, the upper volumetric cavity and the lower volumetriccavity have dissimilar volumes.

In an embodiment of the above invention, an initial gas pressure of thelower volumetric cavity and an initial gas pressure of the uppervolumetric cavity are substantially similar. In some embodiments, themethod also includes forming a plurality of displacement sensorsadjacent to the membrane cover, wherein the plurality of displacementsensors are configured to determine a displacement of the membrane covertowards the upper volumetric cavity or towards the lower volumetriccavity. In an embodiment, the plurality of displacement sensors comprisecapacitors.

In another embodiment, the above method also includes, prior to theforming of the membrane cover, forming sidewall structures upon thesemiconductor substrate, in which the sidewall structures enabledefinition of the lower volumetric cavity. In another embodiment, themethod also includes forming a capping structure from anothersemiconductor substrate, wherein the capping structure comprises aplurality of sidewall structures upon the other semiconductor substrate,wherein the sidewall structures enable definition of the uppervolumetric cavity.

In some embodiments of the above invention the forming of the membranecover comprises forming the membrane cover upon a portion of thesemiconductor substrate within a first low pressure environment. In anembodiment, the coupling of the capping structure comprises coupling thecapping structure to the membrane cover within a second low pressureenvironment, and the first low pressure environment and the second lowpressure environment are substantially similar. In an embodiment, thefirst low pressure environment is approximately a vacuum.

According to other embodiments of the present invention, a method formonitoring MEMS device fabrication processes includes receiving asemiconductor substrate having a plurality of CMOS devices formedthereon, wherein the semiconductor substrate includes an upper surface,wherein the upper surface of the semiconductor substrate is associatedwith an outgassing characteristic, wherein a membrane cover is formedupon at least a portion of the semiconductor substrate, wherein themembrane cover includes an upper surface and a lower surface, whereinthe lower surface of the membrane cover and a portion of the uppersurface of the semiconductor substrate enable definition of a bottomvolumetric cavity, and wherein a capping structure is coupled to themembrane cover at a bonding interface, wherein the bonding interface isassociated with a leakage characteristic, wherein the capping structureincludes a lower surface, wherein the upper surface of the membranecover and the lower surface of the capping structure enable definitionof an upper volumetric cavity, and wherein the upper volumetric cavityand the lower volumetric cavity are separated by the membrane cover.

In an embodiment of the above method, an initial gas pressure of thelower volumetric cavity and an initial gas pressure of the uppervolumetric cavity are substantially similar. In another embodiment, achange in pressure in the upper volumetric cavity with respect tochanges in pressure in the lower volumetric cavity are determined by aplurality of displacement sensors adjacent to the membrane cover. Inanother embodiment, the semiconductor substrate comprises sidewallstructures, and wherein the sidewall structures enable definition of thelower volumetric cavity. In another embodiment, the capping structurecomprises a plurality of sidewall structures, wherein the plurality ofsidewall structures enable definition of the upper volumetric cavity.

In some embodiments of the above method, the upper volumetric cavity isinitially associated with a first low pressure environment. In anotherembodiment, the lower volumetric cavity is initially associated with asecond low pressure environment, and the first low pressure environmentand the second low pressure environment are substantially similar. Inanother embodiment, wherein the first low pressure environment isapproximately a vacuum.

In another embodiment of the above method, the upper volumetric cavityand the lower volumetric cavity have dissimilar volumes. In anotherembodiment, the method also includes reporting a change in pressure,wherein the reporting of change in pressure comprises outputting achange in capacitance value.

It is also understood that the examples and embodiments described hereinare for illustrative purposes only and that various modifications orchanges in light thereof will be suggested to persons skilled in the artand are to be included within the spirit and purview of this applicationand scope of the appended claims.

What is claimed is:
 1. A method for fabricating an integrated MEMS(Micro Electro Mechanical System) device comprising: receiving asemiconductor substrate having a plurality of CMOS devices formedthereon, wherein the semiconductor substrate includes an upper surface,and wherein the upper surface of the semiconductor substrate isassociated with an outgassing characteristic; forming a material layeron top of the semiconductor substrate, wherein the material layerincludes a first lower cavity and a second lower cavity; forming a MEMSmaterial layer comprising a first MEMS device on top of the first lowercavity and a second MEMS device on top of the second lower cavity;forming a capping structure comprising a plurality of caps including afirst upper cap and a second upper cap, wherein forming the cappingstructure includes: receiving a capping structure, forming a dielectriclayer above a surface of the capping substrate, and etching portions ofthe dielectric layer to expose portions of the surface of the cappingsubstrate and to form the first upper cap and the second upper cap;coupling the capping structure to the MEMS material layer at a bondinginterface, wherein the first upper cap and first lower cavity from afirst MEMS cavity, wherein the first MEMS device is disposed therein,wherein the second upper cap and the second lower cavity form a secondMEMS cavity, wherein the second MEMS device is disposed therein, whereinthe first MEMS cavity is separate from the second MEMS cavity; andwherein the outgassing characteristic of the semiconductor substratecauses a gas pressure of the first MEMS cavity to be different from agas pressure of the second MEMS cavity.
 2. The method of claim 1 whereinan initial gas pressure of the first MEMS cavity and an initial gaspressure of the second MEMS cavity are substantially similar.
 3. Themethod of claim 1 wherein a volume of the first MEMS cavity is differentform a volume of the second MEMS cavity.
 4. The method of claim 1wherein the first MEMS device comprises a gyroscope; and wherein thesecond MEMS device comprises an accelerometer.
 5. The method of claim 1wherein a volume of the first lower cavity is substantially similar to avolume of the second lower cavity.
 6. The method of claim 1 wherein avolume of the second upper cap is less than a volume of the first uppercap.
 7. The method of claim 6 wherein a depth of the second upper cap isless than a depth of the first upper cap.
 8. The method of claim 1wherein the forming of the material layer on top of the semiconductorsubstrate comprises forming a dielectric layer above the upper surfaceof the semiconductor substrate; and etching portions of the dielectriclayer to expose portions of the upper surface of the semiconductorsubstrate and to form the first lower cavity and the second lowercavity.
 9. A method for fabricating an integrated MEMS (Micro ElectroMechanical System) device comprising: receiving a semiconductorsubstrate having a plurality of CMOS devices formed thereon, wherein thesemiconductor substrate includes an upper surface, and wherein the uppersurface of the semiconductor substrate is associated with an outgassingcharacteristic; forming a material layer on top of the semiconductorsubstrate, wherein the material layer includes a first lower cavity anda second lower cavity; forming a MEMS material layer comprising a firstMEMS device on top of the first lower cavity and a second MEMS device ontop of the second lower cavity; forming a capping structure comprising aplurality of caps including a first upper cap and a second upper cap,wherein the forming of the capping structure comprises: receiving acapping substrate, forming a dielectric layer above a surface of thecapping substrate, and etching portions of the dielectric layer toexpose portions of the surface of the capping substrate and to form thefirst upper cap, wherein the second upper cap is not exposed to portionsof the surface of the capping structure, coupling the capping structureto the MEMS material layer at a bonding interface, wherein the firstupper cap and first lower cavity from a first MEMS cavity, wherein thefirst MEMS device is disposed therein, wherein the second upper cap andthe second lower cavity form a second MEMS cavity, wherein the secondMEMS device is disposed therein, wherein the first MEMS cavity isseparate from the second MEMS cavity; and wherein the outgassingcharacteristic of the semiconductor substrate causes a gas pressure ofthe first MEMS cavity to be different from a gas pressure of the secondMEMS cavity.